This invention relates generally to bar clamps of the type used to temporarily clamp two articles together, for example, for gluing, or to hold a work-piece for welding or other operation, and more particularly to a quick-action bar clamp wherein the moving jaw is normally spring-biased toward the stationary jaw by a self-contained tension spring.
Bar clamps of the various configurations are old and well-known. A relatively recent entry into the prior art is the quick-action bar clamp disclosed in U.S. Pat. Nos. 4,926,722 and 5,005,449 and marketed by Peterson Manufacturing Co., Inc. as its "Quick-Grip" clamp. The clamp has a movable jaw which is rapidly movable over both short and long distances to clamp against a workpiece, and is operable with one hand. The movable jaw is connected to one end of a movable slide bar and a stationary jaw is supported on the slide bar by a support structure including a trigger handle grip which releasably engages the slide bar and advances the movable jaw toward the fixed jaw. The trigger mechanism provides a one-way drive which normally precludes moving the slide bar and movable jaw away from the fixed jaw; the movable jaw can be moved in the opposite direction only when the one-way drive mechanism is disengaged.
A disadvantage in the "Quick-Grip" clamp lies in the fact that once the jaws are initially clamped against a work-piece the construction of the lever mechanism is such that the hand cannot exert sufficient force on the trigger handle to advance the movable jaw by another increment, with the consequence that the clamp lacks the power to adequately clamp two articles together.
In other known forms of bar clamps the moving jaw is entirely disengaged and free to move on one or more slide bars until the final tightening of an object between the movable and fixed jaws is accomplished, making its use cumbersome and imprecise.
Thus, there is a need for a bar clamp having a movable jaw which is rapidly movable from any point on a slide bar to clamp a work-piece against a fixed jaw and is capable of providing large clamping forces.